Enter about:support in the address bar, go to the Graphics section and check WebGL 1 Driver Renderer

I have this problem on and off. It seems to start happening when I've asked my computer to do too much photo editing on Canva or while editing my Wix website. The only thing I've found to help is to clear Firefox's cache, then restart the browser. Alternatively, I have had the same issue on Chrome, but not as often so I will sometimes switch to that browser. I default to Firefox though. My computer *shouldn't* in theory have issues rendering the photo editing online. It doesn't have amazing specs, but it has more than enough RAM, graphics, etc.